[Elecraft] SSB RF problems on 20 Meters Only

[Don Wilhelm]

Ron,

You correct that you need a common mode choke - maybe one at the antenna 
and another at the point where the coax enters the house.

However, you cannot create that choke by winding wire around the coax, 
but you can wind the coax through a toroid core.
See the information given by Jim Brown K9YC at 
<http://audiosystemsgroup.com/RFI-Ham.pdf>
If you only want a few of the mix 31 toroids, they can be found at Parts 
and Kits <http://www.partsandkits.com/>.

73,
Don W3FPR

On 11/18/2012 12:59 PM, Ron Gruner wrote:
> I am getting RF interference when SSB on 20 meters on my Elecraft K3.  A
> warble in the audio (with either the speaker or headphones) starts at about
> 5 watts which gets much worse as I increase power to the point the audio is
> just a screech.  It works fine on CW.  I have no problems on other bands
> both above and below, just 20 meters on SSB.  I still get the distortion on
> the sidetone with audio and RF gain turned to the minimums.
>
> My antenna is an Ultimax DXpedition with a buried ground plane and a six
> foot ground rod attached to the start of the ground plane wiring.  I
> wrapped about 50 turns of #16 stranded around the feed coax close to the
> antenna junction box as a choke, and also attached a 17.3 foot wire off the
> ground plane to resonate at 14.15 MHz as a friend suggested.  Nothing
> helped.
>
> I've only been licensed since July, so this is all new to me.  Thanks for
> any help.
>
>